1. Field of the Invention
The present invention relates to stacked semiconductor devices and methods for fabricating the same, and more particularly, to a stacked semiconductor device and a method for fabricating the same, wherein the method comprises bending and stacking up semiconductor chip-embedded flexible packaging substrates.
2. Description of the Prior Art
Owing to development of semiconductor packaging technology, semiconductor packages nowadays come in a variety of forms. Known methods for packaging semiconductor devices involve mounting an integrated circuit-laden semiconductor chip on a packaging substrate or a lead frame, electrically connecting the semiconductor chip to the packaging substrate or the lead frame, and encapsulating the packaging substrate with encapsulant. Known semiconductor packages are typically modularized using multi-chip module (MCM) in order to enhance electrical functions of a semiconductor chip, meet the packaging requirements for integration and miniaturization of semiconductor packages, enhance the performance and capacity of a single semiconductor package, and get in line with the trend toward miniaturization, high capacity, and high speed of electronic products. Also, multi-chip modularization downsizes semiconductor packages and enhances electrical functions thereof and therefore has become a mainstream packaging technology. Multi-chip modularization involves mounting at least two semiconductor chips on a chip carrier of a single package, with each of the two semiconductor chips being stacked on the chip carrier. Also, to enhance the electrical functionality of a semiconductor device, semiconductor manufacturers developed a semiconductor package (Package on Package) technology which involves electrically connecting two semiconductor packages (a semiconductor package comprising a semiconductor chip and a carrier, and another semiconductor chip package of a different type or with electrical functionality different from that of the aforesaid semiconductor package) to one another by conductive components, such as solder balls, so as to provide enhanced electrical functionality. Semiconductor devices of this kind are commonly known as stacked package on package.
Referring to FIGS. 1A through 1C, which are cross-sectional views of a fabrication method disclosed in U.S. Pat. No. 6,879,047, a flexible substrate 10 with a first surface 10a, an opposing second surface 10b, and a plurality of openings 100 formed therein to penetrate the first and second surfaces 10a, 10b is provided. A plurality of connecting pads 101 are formed at one end of corresponding ones of the openings 100, respectively, so as to be electrically connected to the flexible substrate 10. As shown in the drawings, at least a first semiconductor package 11 and at least a second semiconductor package 12 are provided. The first semiconductor package 11 comprises a packaging substrate 110 and first and second semiconductor chips 111, 112 mounted on a surface of the packaging substrate 110. The first and second semiconductor chips 111, 112 are electrically connected to the packaging substrate 110 by a plurality of metal wires 113. The metal wires 113 and the first and second semiconductor chips 111, 112 are encapsulated by an encapsulant 114. A plurality of conductive components 115 are formed on another surface of the packaging substrate 110. The second semiconductor package 12, which has the same structural features as the first semiconductor package structure 11, comprises a packaging substrate 120 and first and second semiconductor chips 121, 122 mounted on a surface of the packaging substrate 120. The first and second semiconductor chips 121, 122 are electrically connected to the packaging substrate 120 by a plurality of metal wires 123. The first and second semiconductor chips 121, 122 and the metal wires 123 are encapsulated by an encapsulant 124. A plurality of conductive components 125 (shown in FIG. 1A) are formed on another surface of the packaging substrate 120. The first and second semiconductor packages 11, 12 are electrically connected to the connecting pads 101 on the flexible substrate 10 via the conductive components 115, 125, thereby allowing the first semiconductor package 11 to be electrically connected to the second semiconductor package 12 via the flexible substrate 10 (shown in FIG. 1B). The first semiconductor package 11 is flipped over to be superimposed on the second semiconductor package 12 such that the first semiconductor package 11 is stacked on the second semiconductor package 12. The first and second semiconductor packages 11, 12 are electrically connected to one another by the flexible substrate 10, and a plurality of solder balls 13 are formed on the bottom surface of the flexible substrate 10 so as to be electrically connected to another electronic device (shown in FIG. 1C), allowing a stacked semiconductor device to be formed.
The steps of mounting the first semiconductor chips 111, 112 and the second semiconductor chips 121, 122 on the packaging substrates 110, 120, proceeding to encapsulation, and electrically connecting the first and second semiconductor packages 11, 12 to one another by the flexible substrate 10 are intricate and difficult, because the steps entail an encapsulation process, stacking, and electrical connection. Also, with the first and second semiconductor packages 11, 12 mounted on the flexible substrate 10, the packages are tall, rather than short, and in consequence the stacked semiconductor device fabricated is rather tall to the detriment of miniaturization.
Accordingly, an issue that calls for immediate solution involves solving the drawbacks of the prior art, namely unfavorably great height of conventional stacked semiconductor devices and an intricate fabrication process thereof.